High resolution analytical instruments are capable of measuring the physical and chemical properties of materials with great accuracy. Such analysis plays an important role in modern manufacturing processes by ensuring that starting materials meet all required specifications. The accuracy of high resolution instruments, however, can be diminished by sample related effects.
For example, it often is important to determine the density, refractive index, and other physical and chemical properties of liquids that will be used in a manufacturing process. Such properties, however, are temperature dependent. Thus, if the temperature of samples is not carefully and reproducibly controlled, even the most sophisticated instrument will provide inaccurate and inconsistent measurements.
The analytical instruments themselves are capable of maintaining the temperature of a sample, but typically have relatively limited capacity to adjust sample temperatures rapidly. It is important, therefore, that samples be introduced into an instrument at or very near the desired analytical temperature. Frequently, however, they are not. At times, they are introduced at greatly differing temperatures. When that happens the instrument may take a relatively long time to adjust the temperature of a sample. As the time required for temperature adjustment increases, so does the time required to analyze multiple samples.
For example, some analytical instruments, such as the melting/boiling point determination instrument disclosed in U.S. Pat. No. 5,874,667 to D. Kasman, utilize a metallic heater block. Samples are loaded in vials, and the vials are placed in cavities in the heater block. The temperature of the heating block, however, can take a long time to adjust if the temperature must be lowered. Moreover, sample fluids are loaded in vials, and thus the device cannot monitor the temperature of the sample directly. Vial contamination also is a significant issue. Cleaning and reusing vials may be difficult and time consuming. It also can involve added expense, as will the use of single-use vials.
Various devices, therefore, have been devised for preheating samples so that they may be introduced into an analytical instrument at or very near the desired analysis temperature. Prior art sample preheating devices typically utilize a temperature controlled fluid bath, such as a water or oil bath. Samples are loaded into vials, and the vials are immersed in the bath for a period of time before introducing the sample into an analytical instrument.
Fluid bath preheaters are widely used and are generally effective in bringing a sample to a desired temperature, but they suffer a number of deficiencies. They require the installation and maintenance of basins, fluid lines, pumps, and the like. Bath fluids, or their additives, also can present safety issues if users are accidentally exposed to them, especially since the bath may be at elevated temperatures. Moreover, bath preheaters require a relatively large supply of clean, uncontaminated vials, and because the sample is in a vial, it generally is not practical to measure the temperature of a sample directly.
The prior art, therefore, to date has failed to adequately and simultaneously address various issues relating to the performance, design, use, and fabrication of sample preheating devices. For example, it is essential that sample preheaters be able to rapidly and accurately process a series of samples, even when the samples are different or have different analysis temperatures. Thus, the temperature of samples introduced into a preheater must be easily, accurately, and quickly controlled. Any delay in adjusting the temperature of samples in the preheater will cause a corresponding delay in the ultimate analysis of samples. It also is important that issues of sample contamination and cleaning be addressed in an effective, cost efficient manner and without introducing further delay in processing different samples. Moreover, once a sample has been brought to the desired analysis temperature, its temperature must be maintained until the sample is delivered to the analytical instrument.